Unit, assembly, device and method for testing a sensor means provided in a medical localisation device

ABSTRACT

A unit, assembly and device suitable for a medical localization device suitable for localizing a region in a body with a distal hollow needle includes a tube extending from a proximal first end to a distal second end. The first end is designed to be in communication with a fluid filled container. The unit includes a first part of sensor means. The first part is a sensor interface, in which the sensor interface is provided to the tube between the first end and the second end. The sensor interface is suitable for observation of the pressure in a fluid in the tube that is in communication with the fluid in the container. The unit includes a closing device distally with respect to the sensor interface for varying the pressure in the fluid in the tube, in which the sensor interface is a membrane.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending application Ser. No.13/260,984, filed Jan. 12, 2012, which is a National Stage applicationof International Application No. PCT/NL2010/000061, filed Apr. 1, 2010,which claims the benefit of Netherlands Application No. 2002708, filedApr. 2, 2009. The entire disclosure of each of the foregoingapplications is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to a unit, assembly, device and a methodfor testing a sensor means provided in a medical localization devicesuitable for localizing a region in a body, such as an anatomical cavitywith a distal hollow needle.

BACKGROUND OF THE INVENTION

Locating an anatomical cavity in a body, for example the body of apatient, is important, inter alia, for anesthetics, in which it is oftennecessary for substances which have an anesthetic action to beintroduced into the anatomical cavity, such as for example the epiduralcavity which is located in the vicinity of the spinal cord. To locatethe anatomical cavity, it is generally known to use a medicallocalization device such as a hollow needle and a reservoir filled withan isotonic liquid or with a gas mixture, and often an injection syringewith a displaceable plunger. When the point of the hollow needle reachesthe anatomical cavity, the fluid flowing out of the needle is no longersubject to any resistance from surrounding tissue, and the pressure inthe liquid drops. The person who is handling the assembly can feel thisin the hand which he is using to operate the injection syringe. Thesepressure variations during handling of the assembly can also be fed backto the user by means of pressure information presented on a screen or bysound. For this purpose the assembly is provided with sensor means thatmeasure the pressure variation of the liquid and generate apressure-signal.

An example of an apparatus for locating anatomical cavities is disclosedinter alia in EP 0 538 259.

The known apparatus comprises a hollow needle, a fluid-filled reservoirwhich is in communication with the needle, pump means for pressurizingthe fluid, measuring means for creating a pressure-measurement signalwhich is related to the pressure prevailing in the fluid,signal-conversion means for converting the pressure-measurement signalcreated by the measuring means into a form which is suitable for furtherprocessing, and reproduction means for emitting an acoustic signal whichis related to the pressure-measurement signal which has been convertedby the signal-conversion means.

The needle of the known apparatus is intended to be introduced into abody and is connected to the reservoir in the form of an injectionsyringe. The injection syringe contains fluid in the form of an isotonicliquid. The needle and the injection syringe are in communication withone another via a T-shaped connector. The pressure-measuring means,which are used to detect and measure the pressure prevailing in theliquid in the injection syringe are also connected to this T-shapedconnector and is in communication with the needle and injection syringe.The known apparatus also comprises a processor for processing apressure-measurement signal created by the pressure-measuring means, inorder that the rate of pressure variation can always be determined whenin communication with the needle and the injection syringe, whichpressure variation is primarily the consequence of the different tissueencountered when moving the needle in the body.

When the known apparatus is being used, the starting point is asituation in which the point of the needle is already situated in thevicinity of the cavity which is to be located. The needle, the injectionsyringe and the pressure-measuring means are set in communication to oneanother by changing the position of a switch in the T-shaped connector.In the injection syringe there is a plunger which functions as a pumpmeans for displacing the liquid through the needle and thus producespressure in the liquid. The pressure which is shown on the screen whenthere is no pressure being exerted on the plunger of the injectionsyringe is calibrated to zero. Then, the person who is handling theinjection syringe and the needle brings the pressure in the liquid inthe injection syringe to a defined level by exerting pressure on theplunger. During this process, he can read the level of the pressure fromthe screen at any time. When the liquid in the injection syringe hasbeen brought to the required pressure, the person who is handling thedevice can move the needle towards the cavity in the body while usingthe pressure data displayed on the screen to carefully maintain apressure on the plunger. When the level of the pressure variationexceeds a minimum level stored in the processor and/or the pressurevariation rate over a defined time period is within minimum marginsstored in the processor, the warning means are activated and emit afirst, acoustic warning signal via acoustic reproduction means. If thepressure can be restored by slightly displacing the plunger, withoutfurther displacement of the needle, the first acoustic warning signalwill stop. On the other hand, if a more abrupt pressure variation occursand the pressure cannot be restored by displacing the plunger, thewarning means emit a second acoustic warning signal, which clearlydiffers from the first warning signal. From the second warning signal,the person who is handling the device can infer that the point of theneedle has reached the anatomical cavity and the he must stop moving theneedle.

A drawback of the apparatus and method which are known from EP 0 538 259is that it is unknown to the person who is handling the injectionsyringe if the measuring means and/or the signal-conversion means areworking correctly. If the measuring means and/or the signal conversionmeans are defect, for example they give erroneous output or do not workat all, the instantaneous pressure data on the screen is shown wrongly.Moreover, emitted acoustic warning signals do not match with the actualpressure. It may also be possible that no warning signal is emitted atall even when the level of the pressure variation exceeds the minimumlevel stored in the processor and/or the pressure variation rate over adefined time period is within the minimum margins stored in theprocessor. This results in a handling of the syringe that can bedangerous. For example, the person who handles the syringe will pass theneedle beyond the cavity and affect the spinal cavity or spinal cord,which have particularly adverse results for the patient.

SUMMARY OF THE INVENTION

It is an object of the invention to at least partially eliminate atleast one of the abovementioned drawbacks or to at least provide ausable alternative.

In particular, it is an object of the present invention to provide animproved unit for testing a sensor means provided in a medicallocalization device in which the above drawback is eliminated or atleast reduced.

According to the present invention, the above object is achieved byproviding a unit according to the present invention. The unit issuitable for a medical localization device. The medical localizationdevice is suitable for localizing a region in a body with a distalhollow needle. The unit comprises a tube extending from a proximal firstend to a distal second end. The first end is designed to be incommunication with a fluid filled container. The unit further comprisesat least a first part of sensor means. This first part is a sensorinterface, in which the sensor interface is provided to the tube betweenthe first end and the second end. The sensor interface is suitable forobservation of the pressure in a fluid in the tube. The fluid in thetube is in communication with the fluid in the container. Furthermore,the unit comprises a closing device distally with respect to the sensorinterface for varying the pressure in the fluid in the tube, in whichthe sensor interface is a membrane.

Having a closing device according to the present invention allows thepressure in the tube to be varied in a controlled and known manner. Theperson who handles the closing device thereby is able to control thepressure in the tube. Having this control allows him to test the medicallocalization device as the actual pressure and/or pressure variation inthe tube is controllable and known. Testing comprises the comparisonbetween the known actual pressure and/or pressure variation and theoutput of the sensor means. The result of the comparison isrepresentative for the operation of the sensor means. The region in thebody can for example be an anatomical cavity. The fact that the sensorinterface is a membrane allows an easy to manufacture structure of thetube. The membrane is located nearby or on an outer wall of the tubeinstead of substantially inside the tube. Therefore, there is no needfor a more complicated construction that holds a sensor interface inplace inside the tube and/or transferring the output of the sensorinterface outside the tube. Moreover, the membrane has an extra functionbesides providing an observation of the pressure. As the membrane islocated nearby or on the outer wall it is replacing the outer wall atthat location. This extra function is keeping fluid inside the tube.This orientation of the membrane allows the side of the membrane facingoutwards (towards for example an ambient) to be accessed easily fromoutside and thus allows an easy interface with the output of the sensorinterface.

In a preferred embodiment of the unit according to the invention theclosing device is provided with an at least partially flexible balloonthat is in open communication with the tube, in which the balloon closesthe tube on pressure when the balloon is compressed.

The fact that an at least partially flexible balloon is used to closethe tube on pressure makes it easy for the user of the medicallocalization device to close the tube on pressure. The balloon can becompressed single handed as only compressing the balloon is needed. Theother hand can still be used to hold the medical localization device inplace.

In a further preferred embodiment of the unit according to the inventionthe tube is divided in a first tube portion and a second tube portion,in which the balloon provides a communication between the first tubeportion and the second tube portion.

The fact that the balloon communicates in between the first tube portionand the second tube portion results in an easy to manufacture tube.Moreover, it allows the balloon to be symmetrical around thelongitudinal axis of the tube portions. Therefore there is no need torotate the unit along its longitudinal axis in order for a hand to reachthe balloon and successively compress the balloon.

In an alternative preferred embodiment of the unit according to theinvention an opening is provided in the outer wall of the tube throughwhich the balloon extends, such that the balloon defines an inner partand an outer part, in which the inner part closes the tube on pressurewhen the outer part is compressed.

The fact that the inner part closes the tube on pressure when the outerpart is compressed allows the tube to be formed in one part having onlya relatively small opening in order for the balloon to fit in. Moreover,it allows a more regulated closing of the tube. The inner part of theballoon closes the tube due to an expansion of the inner part. Thisexpansion can be regulated accurately by compressing the outer part ofthe balloon by hand. The relation between the amount and form ofexpansion of the inner part of the balloon and the compression of theouter part of the balloon can be predefined by choosing a dedicatedshape, orientation and material of the balloon.

In a preferred embodiment of the unit according to the invention theunit comprises first coupling means at the first end, that provide areleasable communication between the fluid filled container and thefirst end of the tube.

This has as advantage that the unit is disposable with respect to thefluid filled container or the fluid filled container is disposable withrespect to the unit. This reduces costs and/or is convenient from acontamination point of view. It also allows a communication withdifferent types of fluid filled containers. For example the fluid filledcontainer can be of different brand, size or interface type and caninclude a pressure means that is automatic or manual.

In a preferred embodiment of the unit according to the invention theunit comprises second coupling means at the second end, that provide areleasable communication between the hollow needle and the second end ofthe tube.

This has as advantage that the unit is disposable with respect to thehollow needle or the hollow needle is disposable with respect to theunit. This reduces costs and/or is convenient from a contamination pointof view. It allows a communication with different types of hollowneedles. For example a hollow needle can be of different brand, size orinterface type. A hollow needle can also contain a handle for bettergrip.

The object of the present invention is also achieved by an assemblyaccording to the present invention, comprising a unit according to theinvention and the hollow needle that is in communication with the secondend of the tube.

In a preferred embodiment of the assembly according to the invention theassembly has the closing device provided to the tube.

This has as advantage that the tube is provided with the at least onepart of the sensor interface and the closing device which result incompatibility with more types of hollow needles. This has as advantagethat the unit is disposable with respect to more types of hollow needlesor more types of hollow needles are disposable with respect to the unit.

The object of the present invention is also achieved by a medicallocalization device according to the present invention, comprising aunit according to the invention, a fluid filled container that is inreleasable communication with the first end of the tube and at least asecond part of the sensor means, the second part being a generator forgeneration of an electric pressure signal that is representative of anobservation from the sensor interface.

It is a further object of the present invention to provide a method fortesting a sensor means in which the drawback of not knowing whether themeasuring means and/or the signal-conversion means are working correctlyis eliminated or at least reduced. This drawback concerns the person whois handling the injection syringe. The sensor means are provided in amedical localization device. The medical localization device is designedfor localizing a region in a body with a distal hollow needle.

The above object is achieved by providing a method according to thepresent invention. This relates to a method for testing a sensor meansprovided in a medical localization device suitable for localizing aregion in a body with a distal hollow needle, in which prior to themethod the medical localization device comprises a closing device in afirst state of the closing device. The method comprises the step ofintroducing a fluid into the medical localization device and the step ofdetermining the pressure in the fluid using the sensor means, in whichthe sensor means generates a pressure signal which is representative ofthe pressure in the fluid. The method furthermore comprises the step ofapplying an elevated pressure to the fluid and the step of operating theclosing device to a second state of the closing device, such that thepressure in the fluid varies. Furthermore, the method comprises the stepof making a first observation of the pressure signal prior to avariation resulting from the operation of the closing device or theappliance of an elevated pressure to the fluid and the step of making asecond observation of the pressure signal after a variation of thepressure in the fluid resulting from the operation of the closing deviceor the appliance of an elevated pressure to the fluid. The methodfurthermore comprises the step of comparing the first observation withthe second observation, in which the comparison is representative to theoperation of the sensor means.

Following the steps of the method of the present invention allows thepressure in the tube to be varied in a controlled and known manner. Theperson who handles the closing device thereby is able to control thepressure in the tube for example by operating the closing device orapplying an elevated pressure. Before one of these steps a firstobservation is made by the sensor means. After one of these steps asecond observation is made by the sensor means. Having this controlallows him to test the medical localization device as the actualpressure and/or pressure variation in the tube is controllable andknown. Testing comprises the comparison between the first observationand the second observation. The result of the comparison isrepresentative to the operation of the sensor means.

In a preferred embodiment of the method according to the invention thesecond state of the closing device is setting a communication betweenthe fluid and an ambient pressure, such that the pressure in the fluiddecreases.

This allows a sequence of steps (among other possible sequences) whereinthe initial first state of the closing device is closed, such that thefluid can stream through the localization device, but not through theclosing device to ambient space. Firstly, an elevated pressure isapplied to the fluid. Secondly, a first observation of the pressuresignal is made. Thirdly, the closing device is operated to the secondstate (ambient). Fourthly, a second observation is made. The pressure inthe fluid should decrease due to the continuing appliance of theelevated pressure and the fluid being in communication with ambientspace. Lastly, the first observation is compared with the secondobservation and is representative to the operation of the sensor means.

In a preferred embodiment of the method according to the invention thesecond state of the closing device is closing the medical localizationdevice from pressure, such that the pressure in the fluid increases.

This allows a sequence of steps (among other possible sequences) whereinthe initial first state of the closing device is an open position, suchthat fluid can stream through the localization device. Firstly, anelevated pressure is applied to the fluid. Secondly, a first observationof the pressure signal is made. Thirdly, the closing device is operatedto the second state (closed). The pressure in the fluid increases due tothe continuing appliance of the elevated pressure and a closed medicallocalization device. Fourthly, a second observation is made. Lastly, thefirst observation is compared with the second observation and isrepresentative to the operation of the sensor means.

In a preferred embodiment of the method according to the invention themedical localization device is provided with a tube and with a fluidfilled container and the method comprises the step of coupling aproximal first end of the tube with the fluid filled container usingfirst coupling means, in which the first coupling means provide areleasable communication between the container and the first end of thetube.

The step of coupling the first end of the tube with the fluid filledcontainer allows a method that can be applied to different kinds offluid filled containers. This allows for flexibility when performing themethod. For example fluid filled containers of different brands ordifferent sizes, shapes or other characteristics can be used. Moreover,it allows the tube to be disposable. The tube can be provided withsensor means and the closing device.

In a preferred embodiment of the method according to the invention themedical localization device is provided with a tube and with the hollowneedle and comprises the step of coupling a distal second end of thetube with the hollow needle using second coupling means, in which thesecond coupling means provide a releasable communication between thehollow needle and the second end of the tube.

The step of coupling the second end of the tube with the hollow needleallows a method that can be applied to different kinds of hollowneedles. This allows for flexibility when performing the method. Forexample, hollow needles of different brands or different sizes, shapes,thickness or other characteristics can be used. Moreover, it allows thetube and/or needle to be disposable. The tube can be provided withsensor means and the closing device.

In a further embodiment of the method according to the invention ahollow needle is at least partly inside the body, such as a human body.

The fact that the hollow needle is inside a human body allows testing ofthe medical localization device during invasion. This gives moreconfidence and safety to the user of the medical localization device.

In an embodiment of the method according to the invention the medicallocalization device is entirely outside a human body.

The fact that the medical localization device is entirely outside ahuman body allows testing before and/or after invasion into a humanbody. When the method is performed before invasion it increasesconfidence for the user and safety in general as the sensor means aretested on their performance before use. When the method is performedafter invasion it ascertains the correct feedback of a monitoring of theinvasion. During invasion the observations made by the sensor means canbe monitored and registered and used for analysis. This analysis can berelevant if additional complications occur and when one wants to knowwhat the origin of such a complication was. The said observations insuch a case are helpful.

These and further embodiments of the unit and the method according tothe invention are described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages of the presentinvention will be explained in more detail by means of the followingdescription of two preferred embodiments of a unit according to theinvention and two preferred embodiments of a method according to theinvention with reference to the drawings, in which identical referencenumerals denote identical components, and in which:

FIG. 1 shows a side view of a first preferred embodiment of a unitaccording to the invention.

FIGS. 2a, 2b and 2c seen consecutively show one possible sequence ofsteps of a first preferred embodiment of the method of the invention.Wherein FIG. 2a shows a side view of the first preferred embodiment ofthe unit of FIG. 1. These sequence of steps are performed outside ahuman body.

FIGS. 3a, 3b and 3c seen consecutively show one possible sequence ofsteps of a second preferred embodiment of the method of the invention.These sequence of steps are performed inside a human body. Wherein FIG.3a shows a side view of a second preferred embodiment of the unit.

FIGS. 4a, and 4b show an alternative embodiment of the unit.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a unit 1 according to the invention. FIG. 1 also shows asystem 2, comprising the unit 1 and a hollow needle 10. Also a medicallocalization device 3 is shown, comprising the unit 1, a fluid filledcontainer 9 and a generator 29.

The unit 1 comprises a tube 4 and has first coupling means 5 on aproximal first end 6 and second coupling means 7 on a distal second end8. Proximal means close to the person who is handling the unit. Distalmeans away from the person who is handling the unit.

The first coupling means 5 provide a releasable communication between afluid filled container 9 and the first end 6. The second coupling means7 provide a releasable communication between a hollow needle 10 with aneedle point 11 and the second end. Therefore, the second coupling means7 allow a communication between the hollow needle 10 and the tube 4. Thehollow needle 10 is provided with a handle 12, which can be held by theperson who is handling the hollow needle 10, for example a physician.The tube 4 comprises a fluid filled space 15.

The fluid filled container 9 is in the form of an injection syringe andis positioned in line with the hollow needle 10. The fluid filledcontainer 9 comprises a fluid-filled space 17 that is in communicationwith the fluid filled space 15 of the tube and a displaceable plunger 18which closes off the said container 9 in a sealed manner on one side.

The unit 1 is provided with at least a first part 19 of sensor means 20,the first part being a sensor interface 21 located between the first end6 and the second end 8. The sensor interface 21 is suitable forobservation of the pressure in the fluid filled space 15 of the tube. Aclosing device 23 is placed distally with respect to the sensorinterface 21. Here, the tube 4 comprises the closing device 23 betweenthe second end 8 and the sensor interface 21. This closing device 23 isin the form of a flexible balloon 24 that is in open communication withboth ends 6, 8 of the tube 2. This flexible balloon 24 divides the tube4 in a first tube portion 25 and a second tube portion 26. The balloon24 provides a communication between the first tube portion 25 and thesecond tube portion 26. When the balloon 24 is pressed, for exampleusing a thumb and an index finger, the balloon 24 closes the tube 4 onpressure at that location such that it at least narrows thecommunication such that a pressure variation can occur. The balloon 24comprises a fluid filled space 27 that is in communication with thefluid filled space 15 of the tube.

The displaceable plunger 18 in this case functions as a pump means forgenerating pressure in the fluid filled spaces 15,17,27 of the tube,container and balloon. The container 9 is in communication with thehollow needle 10 via the tube 4, the balloon 24 and the coupling means5,7, it being possible for fluid to flow out of the container 9 into thehollow needle 10. The fluid in the container 9 may be a gas or a liquid,for example a sterile, isotonic liquid.

To observe the pressure in the fluid the sensor interface 21 is providedwith a membrane 28. An output of the membrane 28 is connected to aninput of a generator 29 that generates electric pressure signals. Thisgenerator is a second part 31 of the sensor means 20. The generator 29is able to convert an observation provided by the membrane 28 into theelectric pressure signal which can be used for further processing. Theelectric pressure signal can be for example an electric voltage. Thiselectric voltage can be used as input for an synthesizer 33 thatgenerates sounds through a loudspeaker 35 that is representative to theobserved pressure. An alternative to the synthesizer is displaying theelectric voltage on a screen 37 after it has been amplified by anamplifier 38. In FIG. 1 the membrane 28 and the generator 29 areseparate elements, making the unit 1 disposable at lower recurrent priceas the generator 29 is not part of the unit 1.

FIGS. 2a, 2b and 2c show a sequence of the use of the first preferredembodiment of unit 1 shown in FIG. 1.

The sensor means 20 can be tested by performing the steps of a firstpreferred embodiment of the method according to the invention. The unit1 is entirely outside a human body, before the needle 10 enters thehuman body, as shown in FIG. 2a and the balloon 24 is in an openposition. Firstly, an elevated pressure in the fluid is applied bymoving the plunger 18 (not shown in the figures). The pressure willbuilt up in the fluid and as a result of this pressure, the fluid willtend to flow out via the needle point 11. The sensor means 20 shallprovide a pressure signal according to the actual pressure in the tube4. This pressure is observed in a first observation of the user.Secondly, as is shown in FIG. 2b by means of arrows, the balloon 24 ispressed such that it closes the tube 4. This results in an increase ofthe pressure in the fluid between the balloon 24 and the plunger 18.When the plunger 18 is continued to be applied, which is shown in FIG.2c by means of an arrow, the pressure shall continue to increase. Theincreased pressure is observed in a second observation of the user.Thirdly, the first observation and the second observation are comparedby the user and is representative for the operation of the sensor means20. As the user knows that closing the tube 4 on pressure results in anincrease of pressure between the plunger 18 and the balloon 24, heexpects to have this feedback from the sensor means 20. If the expectedfeedback is not observed this is an indication that the sensor means 20are not functioning correctly.

FIGS. 3a, 3b and 3c show a unit lb in a second preferred embodiment ofthe invention. The unit lb is largely equal to the unit 1 as shown inFIG. 1. Similar components are denoted with the same numerals as in FIG.1, except for the closing device 23 that is not provided with a balloon24, but with a switch, such as a valve 40. FIGS. 3a, 3b and 3c seenconsecutively show one possible sequence of steps of a second preferredembodiment of the method of the invention. In FIG. 3a the unit lb of thesecond preferred embodiment shows specifically its use for locating ananatomical cavity 44, in particular the epidural cavity, in a humanbody. A small section of a human body is illustrated in cross section inFIG. 3a and is denoted by reference numeral 42. The anatomical cavity orepidural cavity is denoted by reference numeral 44. The needle point 11is situated in the vicinity of the epidural cavity 44.

In this second preferred embodiment the closing device 23 is in the formof a switch or valve 40. The valve 40 has two states. In one state thevalve 40 is closed and no communication via the valve 40 is made betweenthe tube 4 and ambient pressure. When in the other state the valve 40 isopen and there is a communication via the valve 40 between the tube 4and ambient pressure.

The sensor means 20 can be tested. Firstly, an elevated pressure in thefluid is applied by moving the plunger 18 as shown in FIG. 3b . Thepressure will be built up in the fluid and as a result of this pressure,the fluid will tend to flow out via the needle point 11. The valve 40 isclosed. Depending on where the needle point 11 is situated a certainresistance is expressed as pressure which has to be overcome by theperson who is exerting a force on the plunger 9. For example, the needlepoint 11 can be located outside or inside a body tissue. The sensormeans 20 shall provide a pressure signal accordingly. This pressure isobserved in a first observation of the user. Secondly, as is shown inFIG. 3c , the valve 40 is set to open and the tube 4 is communicationwith ambient pressure. This results in a decrease of the pressure in thefluid between the valve 40 and the plunger 18. The decreased pressure isobserved in a second observation of the user. Thirdly, the firstobservation and the second observation are compared by the user and isrepresentative for the operation of the sensor means 20. As the userknows that opening the valve 40 results in a decrease of pressurebetween the plunger 18 and the valve 40, he expects to have thisfeedback from the sensor means 20. If the expected feedback is notobserved this is an indication that the sensor means 20 are notfunctioning correctly.

FIGS. 4a and 4b show an alternative embodiment of a unit 1 c. The unit 1c is largely equal to the unit 1 as shown in FIG. 1. Similar componentsare denoted with the same numerals as in FIG. 1, except for the closingdevice 23 that is now provided with a balloon 46 that extends throughthe outer wall 47 of the tube 4. The balloon 46 defines an inner part 48and an outer part 49. When the outer part 49 is compressed, as shown inFIG. 4b , the inner part 48 closes or at least narrows the tube 4, suchthat a pressure variation can occur. Arrows in FIG. 4b , show thecompression of the outer part 49. For example, the compression resultsby applying a force in line with the arrows using an index finger and athumb.

The invention is not limited to the described embodiments.

Alternatively, the closing device 23 does not closes the tube 4 entirelybut closes the tube 4 at least partly or narrows the tube 4, such that apressure variation still occurs.

As an alternative to using a plunger 18 as the pump means, it is alsopossible, for example, to use bellows or mechanical operated pumpingmeans, such as electric pump means.

An alternative to a membrane 28 is an electrical pressure gauge.

Alternatively, the membrane 28 and the generator 29 form a single unitinstead of two separate elements.

Alternatively, the tube is made of any suitable material and is madefrom a material that is stiff or is made from a material that isflexible.

In an alternative, the tube is made of multiple parts.

In another alternative, the tube has different types of shape, forexample bended with a sharp edge or a smooth edge. In an example, thetube is T-shaped.

In an alternative, the unit comprises third part of sensor means. In anexample the first part of sensor means, the first part being a sensorinterface, is in communication with a second part of the sensor means,the second part being a generator, through a third part of sensor means,the third part being a hose or another tube. In this alternative thefirst part of sensor means can be located on a distance from the secondpart of sensor means.

In an alternative to the first preferred embodiment of the method, theballoon 24 is pressed before the plunger 18 is applied. The firstobservation is made before the plunger 18 is applied and the secondobservation is made after or during the appliance of the plunger 18. Thelast step is the comparison between the first observation and the secondobservation.

In an alternative, the closing device is a valve.

In an alternative, the closing device is provided integrally to the tubeat a location distal from the sensor means where the tube is designed tobe weakened or softened. For example, the tube is made of a flexiblematerial which is weak or soft and can be pressed together such that itcloses off the tube distally from the sensor means.

In an alternative to the first preferred embodiment of the method, thesteps are performed with the hollow needle 10 at least partly inside abody, such as a human body.

In an alternative to the first preferred embodiment of the method, thesteps are performed without the unit 1,1 b being connected to the hollowneedle 10.

Alternatively, the first- and second coupling means 5, 7 can bestandardized couplings or dedicated couplings. Standardized couplingsprovide a coupling of for example Luer needles and/or containers withthe unit 1,1 b. Other standards are possible too.

In an alternative, the sensor means 20 comprises the synthesizer 33, theloudspeaker 35, the amplifier 38 and the screen 37.

A unit according to the invention is foreseen, wherein the first end ofthe tube communicates integrally with the fluid filled container.

This has as advantage that the unit and fluid filled container form awhole and are integrated which has as advantage that there is no need toconnect the fluid filled container to or release the fluid filledcontainer from the unit. This saves time and reduces possible errors,such as connecting the wrong fluid filled container to the unit.

Also a unit according the invention is foreseen, wherein the second endcommunicates integrally with the hollow needle.

This has as advantage that the unit and the hollow needle form a wholeand are integrated which has as advantage that there is no need toconnect the hollow needle to or release the hollow needle from the unit.This saves time and reduces possible errors, such as connecting thewrong hollow needle to the unit.

An assembly according to the invention is foreseen, wherein the closingdevice is provided to the hollow needle.

This has as advantage that this location of the closing device ispreferable in terms of easy handling. For example, when the assembly isoperated using a right hand it may be convenient for the user that theclosing device is distal from the right hand. In case a handle islocated between hollow needle and tube this means that it is convenientthat the closing device is provided to the hollow needle.

1. A unit suitable for a medical localization device suitable forlocalizing a region in a body with a distal hollow needle, comprising: atube extending from a proximal first end to a distal second end, whereinthe first end is designed to be in communication with a fluid filledcontainer; at least a first part of sensor means, the first part being asensor interface, in which the sensor interface is provided to the tubebetween the first end and the second end, in which the sensor interfaceis suitable for observation of the pressure in a fluid in the tube thatis in communication with the fluid in the container; and a closingdevice distally with respect to the sensor interface for varying thepressure in the fluid in the tube, in which the sensor interface is amembrane.
 2. The unit according to claim 1, wherein in the closingdevice is provided with an at least partially flexible balloon that isin open communication with the tube, and wherein in which the ballooncloses the tube on pressure when the balloon is compressed.
 3. The unitaccording to claim 2, wherein the tube is divided in a first tubeportion and a second tube portion, and wherein in which the balloonprovides a communication between the first tube portion and the secondtube portion.
 4. The unit according to claim 2, wherein an opening isprovided in the outer wall of the tube through which the balloonextends, such that the balloon defines an inner part and an outer part,and wherein the inner part closes the tube on pressure when the outerpart is compressed.
 5. The unit according to claim 1, further comprisingfirst coupling means at the first end, that provide a releasablecommunication between the fluid filled container and the first end ofthe tube.
 6. The unit according to claim 1, further comprising secondcoupling means at the second end, that provide a releasablecommunication between the hollow needle and the second end of the tube.7. An assembly, comprising: a unit according to claim 1; and a hollowneedle that is in releasable communication with the second end of thetube.
 8. The assembly according to claim 7, wherein the closing deviceis provided to the tube.
 9. A medical localization device, comprising: aunit according to claim 1; the fluid filled container that is inreleasable communication with the first end of the tube; and at least asecond part of the sensor means, the second part being a generator forgeneration of an electric pressure signal that is representative of anobservation from the sensor interface.
 10. A method for testing a sensormeans provided in a medical localization device suitable for localizinga region in a body with a distal hollow needle, in which prior to themethod the medical localization device comprises a closing device in afirst state of the closing device, comprising the steps of: introducinga fluid into the medical localization device; determining the pressurein the fluid using the sensor means, in which the sensor means generatesa pressure signal which is representative of the pressure in the fluid;applying an elevated pressure to the fluid; operating the closing deviceto a second state of the closing device, such that the pressure in thefluid varies; making a first observation of the pressure signal prior toa variation resulting from the operation of the closing device or theappliance of an elevated pressure to the fluid; making a secondobservation of the pressure signal after a variation of the pressure inthe fluid resulting from the operation of the closing device or theappliance of an elevated pressure to the fluid; and comparing the firstobservation with the second observation, in which the comparison isrepresentative to the operation of the sensor means.
 11. The methodaccording to claim 10, wherein a pumping means is provided in themedical localization device for the appliance of an elevated pressure tothe fluid.
 12. The method according to claim 10, wherein the secondstate of the closing device is setting a communication between the fluidand an ambient pressure, such that the pressure in the fluid decreases.13. The method according to claim 10 wherein the second state of theclosing device is closing the medical localization device from pressure,such that the pressure in the fluid increases.
 14. The method accordingto claim 10 wherein the medical localization device is provided with atube and with a fluid filled container and the method comprises the stepof: coupling a proximal first end of the tube with the fluid filledcontainer using first coupling means, wherein the first coupling meansprovide a releasable communication between the container and the firstend of the tube.
 15. The method according to claim 10 wherein themedical localization device is provided with a tube and with a hollowneedle and the method comprises the step of: coupling a distal secondend of the tube with the hollow needle using second coupling means,wherein in which the second coupling means provide a releasablecommunication between the hollow needle and the second end of the tube.16. The method according to claim 14, wherein in which the hollow needleis at least partly inside the body, such as a human body.
 17. The methodaccording to one of the claim 10, wherein in which the medicallocalization device is entirely outside a human body.